The present invention relates to motion picture cameras. More particularly, it relates to motion picture cameras which have photosensitive receiver means which furnish a signal to aperture control means, the photosensitive receiver means being positioned behind the aperture in the path of light falling on the film so that the quantity of light falling on the photoreceiver means is indicative of the quantity of light falling on the film at the particular aperture size. Even more specifically, the present invention relates to motion picture cameras wherein the size of the aperture is controlled by means of a stepmotor which, in turn, has windings energized by a pulse generator. Of course the pulse generator furnishes a pulse sequence to the stepmotor only when the quantity of light falling on the film differs from the desired quantity. Further, the repetition rate of the pulse generator of course determines the rate at which the stepmotor operates and therefore the rate at which the aperture is opened or closed.
A source of error in conventional cameras of this type is the inertia or time-delay behavior inherent in the photoreceiver. This of course should be compensated for in order that the aperture size is correct for the prevailing light conditions.